1. Field of the Invention
The present invention relates to an exposure device which can be applied to the color images forming machine of the thermal type and, more particularly, it relates to an exposure device provided with a device capable of varying the quantity of light shot relative to the plane of the machine on which originals are placed.
2. Description of the Related Art
Color images forming machines of the thermal type are widely used these days they can be grouped into two kinds, one of which is the melting thermal type, providing high resolution, and the other is of the subliming thermal type, making it difficult for images to be erased and corrected. In addition, an image forming machine suitable for forming licenses, certificates and tickets for automatic systems is under development. This machine is intended to form an image on a recording medium according to both the melting and sublimimg thermal techniques so as to make use of the advantages attained by each.
In the case where images are formed according to the melting and subliming thermal techniques, using the image forming machine, however, printing speed according to the subliming thermal manner is slower, as compared with the melting thermal technique. When the quantity of light shot from an exposure light source is made suitable for the melting thermal technique, therefore, it becomes excessive for the subliming manner, making it impossible to form good images.